I thought it was kind of dumb how Rosh wields a red lightsaber when you fight him. I know he's gone to the dark side and all, but how would he have obtained a different lightsaber? I suppose you can think up plausible explanations but I still find it more likely that he would have use his Jedi lightsaber. (Hey, even Darth Vader continued to use his blue saber until his immolation, and he was a Sith!)

Can someone make it so that Rosh's saber is yellow? It should be pretty simple, right?

First of all, Rosh's lightsaber is yellow. Second, this thread should be moved to coding because you only can change the colour throught coding.
And I agree with you, Rosh's lightsaber colour shouldn't have changed.

Second, this thread should be moved to coding because you only can change the colour throught coding.

No. You can change the color of the blade through text editing. All you have to do is change the color in Rosh's NPC file which can be opened and edited with notepad. Unless of course you consider that coding.

You can do it in half the time it would take any one of us to do it for you and send it back to you. Just open the .npc file in notepad and change the color, save, package it up in a new PK3 and voila. Done.